When grinding a workpiece such as a sapphire wafer or a silicon wafer used for manufacturing a semiconductor device, a grinding wheel is fed into the workpiece and grinds it to a mirror-finished state while being rotated at high speed in a surface grinder equipped with a cup grinding wheel.
However, there is a problem in the case of the workpiece being a hard brittle material such as a sapphire wafer that the workpiece cannot be machined with high accuracy at a high machining rate. More specifically, where the workpiece is hard, the edge of the grinding wheel is difficult to work with respect to the workpiece, so that wear of abrasive grains during the grinding is advanced quickly and deterioration of the grinding wheel surface due to glazing, loading, and shedding becomes severe, and the grinding becomes impossible soon. As a result, the grinding wheel alone is worn out or becomes unable to be fed, and consequently, the grinding is carried out at a remarkably low machining rate. A grinding wheel on the order of #1500 or more has a problem that practical grinding of the hard workpiece is not available.
Solutions to this problem include development of a highly sharp grinding wheel and development of a machine with high rigidity allowing the grinding wheel to be fed strongly. In addition to such general solutions, there is a method that rotates the grinding wheel at high speed at a number of revolutions on the order of 6000 rpm to be fed to perform the grinding while supplying a slurry containing fine abrasive grains onto a ground surface of the workpiece (Patent Document 1).